Minimizing power consumption is a significant concern when conducting wireless communications, especially with battery-powered devices (e.g., wireless network devices (e.g., radio frequency (RF) devices), Internet-of-Things (IoT) or Wireless Sensor Network (WSN) devices, etc.). Among various sources of energy consumption, a wireless node's RF transmission is a dominant one. In current communication systems, transmissions are typically sent at a constant power level, and usually a maximum power level. In a wireless network, the distances that a receiving node is away from transmitting nodes when the transmitting nodes transmit data at the same constant transmission power will affect the receive signal strengths at the receiving node for each transmission. An example of this is shown in FIG. 1.
FIG. 1 depicts an example wireless network 100. In FIG. 1, network 100 includes a receiving wireless node 102 (denoted in white) that may receive transmissions from one or more transmitting wireless devices (nodes) (denoted in black) that are at various distances away from receiving node 102, where the transmitting is at a constant transmission power. For purposes of illustration, these distances are denoted by zones A-E, where zone A is at a nearest distance to receiving node 102 and zone E is at a farthest distance from receiving node 102. The zones A-E each represent not only a distance from receiving node 102, but also a receive (RX) signal strength at receiving node 102 when receiving a transmission from a transmitting node in that zone. As can be seen from legend 103, receive signal strengths at receiving node 102 from transmissions of transmitting nodes in zone A are the highest, and the signal strengths weaken progressively the further away the transmitting nodes are from the receiving node. For example, a receive signal strength at receiving node 102 of transmissions from transmitting node 104 in zone B at a distance 108 from receiving node 102 is stronger than a receive signal strength of transmissions from transmitting node 106 in zone E at a farther distance 110 from receiving node 102.
While transmissions at a constant high power may ensure good connectivity and reliability, it may cause increased interference, decreased channel re-use, and a decreased overall lifetime of the battery (if battery-powered). Transmissions at a consistent low power may benefit from higher channel re-use and lower interference, but may result in weak connections and unreliable links, while still consuming high amounts of energy due to losses. Thus, generally, use of constant power for transmissions may lead to inefficient use of energy. In addition, use of constant transmission power may contribute to other communication issues, such as, for example, a near-far problem (where a receiving node may not receive a transmission (or may receive a very weak transmission) from a farther transmitting node when another transmission is transmitted from a nearer transmitting node at the same time and at the same power), an overhearing problem (where a node “hears” or receives transmissions that are not intended for it, which causes unnecessary expenditure of battery energy (if battery-powered) and causes channel bandwidth to not be used to its fullest potential), and/or other problems known by those familiar with this technology.
Current solutions to these issues exist but have their downsides. One approach uses a local mean average (LMA) and mean of neighbor (LMN). This is a node level approach that uses the number of neighbor nodes as a metric. However, the initial phase, or setup, for this approach includes overhead which repeats (wasting energy), and the approach does not consider link quality. Another approach involves power control with black listing (PCBL). This approach is a packet level approach that uses packet reception rate (PRR) as a link quality metric. However, its initial beaconing phase includes overhead, and the PRR is a higher layer metric that takes time to build. A further approach is adaptive transmission power control (ATPC). This approach is also a packet level approach, but it takes spatio-temporal impacts into account and uses received signal strength (RSSI) as a link quality metric. However, this approach also has an initial beaconing phase with energy-wasting overhead and uses complex predictive models and matrix calculations. It also uses a predefined static threshold on the signal strength, which makes the algorithm less versatile in differing environmental conditions. Another approach is on-demand transmission power control (ODTPC), which is also a packet level approach. While it has a short initial phase without overhead, it uses a predefined static threshold on signal strength. Further, both the ATPC and ODTPC approaches use RSSI as a link quality indicator, but RSSI used in this way is not considered very robust, as its values are affected by noise, interference, and/or fading. Furthermore, RSSI and/or PRR used as link quality indicators do not take into account media access control (MAC) layer re-transmissions.
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